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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

31632 results found.

  1. EP251130a: JinShan optical observations
  2. Fermi GRB 251130B: Global MASTER-Net observations report
  3. GRB 251127A: SVOM/GRM observation
  4. EP251130a: Swift-XRT counterpart detection
  5. EP251130a: Global MASTER-Net observations report
  6. EP251130a: COLIBRÍ optical counterpart candidate
  7. EP251129a/GRB 251129A: EP-FXT follow-up observations
  8. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  9. GRB 251128A: AstroSat CZTI detection
  10. GRB 251129A / EP251129a: SAO RAS optical observations
  11. GRB 251126A: SAO RAS optical observations
  12. GRB 251128A: GECAM-B detection
  13. GRB 251128A: SVOM/GRM observation of a long burst
  14. GRB 251128A: Insight-HXMT/HE detection
  15. SVOM GRB 251129A : MASTER optical counterpart detection
  16. GRB 251129A: Swift-XRT afterglow detection
  17. GRB 251129A: Swift ToO observations
  18. GRB 251129A / EP251129a: SVOM/VT optical fading
  19. EP251129a: Global MASTER-Net observations report
  20. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  21. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  22. GRB 251129A: Correction to the position of the optical counterpar
  23. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  24. GRB 251128A: Fermi GBM Observation
  25. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  26. GRB 251126A: Swift-BAT refined analysis
  27. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  28. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  29. Fermi GRB 251128A: Global MASTER-Net observations report
  30. GRB 251127A: Glowbug gamma-ray detection
  31. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  32. GRB 251126A: further SAO RAS optical observations
  33. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  34. GRB 251126A NUTTelA-TAO Early Measurements
  35. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  36. GRB251126A: MAO/AZT-22 optical observations
  37. GRB251126A: Continued optical observation from 1.3m DFOT
  38. GRB 251126A: Swift/UVOT Detection
  39. EP251124a: Pan-STARRS ri-band imaging and photometry
  40. GRB 251126A: Mondy and SAO RAS optical observations
  41. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  42. GRB 251126A: NOT optical observations
  43. GRB 251126A: 1.3m DFOT optical afterglow detection
  44. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  45. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  46. GRB 251125B: GECAM-B detection
  47. Fermi GRB 251127A: Global MASTER-Net observations report
  48. GRB 251126A: Kilonova-Catcher optical afterglow detection
  49. GRB 251126A: Asiago i-band detection
  50. GRB 251126A: Nanshan/HMT optical afterglow detection
  51. Swift GRB 251126A: Global MASTER-Net observations report
  52. GRB 251121A: Fermi GBM Observation
  53. GRB 251126A: GIT discovery of the likely optical afterglow
  54. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  55. EP251124b follow-up observation by EP-FXT
  56. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  57. EP251124b: NOT r- and z-band optical upper limits
  58. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  59. Fermi GRB 251125B: Global MASTER-Net observations report
  60. EP251124b: Global MASTER-Net observations report
  61. EP251124a: Xinglong GWAC-F60A optical observation
  62. EP251124a (EP-WXT trigger 01709248862) is triggered by the known source AWM 7
  63. Fermi GRB 251125A: Global MASTER-Net observations report
  64. EP251124a: NOT r- and z-band optical upper limits
  65. EP251124a: Global MASTER-Net observations report
  66. GRB 251124A: Fermi GBM Localization by automated pipeline
  67. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  68. EP251124a: Optical upper limit with Kinder observations
  69. EP251118A: 6 GHz VLA Detection
  70. Fermi GRB 251124a: Global MASTER-Net observations report
  71. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  72. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  73. EP251124a: GROWTH-India Telescope optical upper limits
  74. GRB 251116C: Swift-XRT confirmation of fading
  75. GRB 251122A/EP251122a: FTW optical and NIR observations
  76. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  77. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  78. EP251118A: 3.6m DOT optical afterglow detection
  79. GRB 251122A / EP251122a: EP-FXT counterpart detection
  80. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  81. GRB 251122A / EP251122a: WFST optical observations
  82. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  83. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  84. GRB 251122A / EP251122a: LCO optical upper limits
  85. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  86. EP251122a: Global MASTER-Net observations report
  87. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  88. GRB 251122A / EP251122a: SVOM detection of a long burst
  89. EP251118a: Continued Optical Detection with Kinder observations
  90. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  91. LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates
  92. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  93. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  94. EP251118a: Xinglong-2.16m optical observation
  95. GRB 251115A: Fermi GBM Observation
  96. EP251118A: 1.3m DFOT optical afterglow detection
  97. GRB 251118A: Swift/UVOT Detection
  98. EP251118a / GRB 251118C: SAO RAS optical observations
  99. GRB 251118A: Glowbug gamma-ray detection
  100. GRB 251118A: Fermi GBM Observation

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